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Edmonton
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Edmonton clear sky chart from 2005-11-05 to 2018-03-11.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.
Observation TypeMinimum conditions for hour to be usableOut of hours
Clear of CloudsTransparencySeeingSky Brightness
Planetary:50%(no limit)Average(no limit)Nighttime Hours
Deep Sky:70%Average(no limit)5.9Nighttime Hours
CCD Imaging:70%Below AveragePoor(no limit)Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

PlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
Night
43%
15965
10%
48971
7%
15937
46%
15937
18%
35103

By Month

MonthDays of MonthPlanetaryData
Pts
Deep Sky
Max 60%
Data
Pts
Both Planetary and Deep Sky
Max 60%
Data
Pts
Either Planetary or Deep SkyData
Pts
CCD ImagingData
Pts
January1st to 15thNight
36%
970
7%
2910
4%
970
38%
970
14%
2244
January16th to endNight
32%
978
14%
3058
9%
978
38%
978
16%
2217
February1st to 15thNight
39%
760
9%
2648
8%
757
43%
757
14%
1932
February16th to endNight
47%
684
12%
2185
12%
684
50%
684
18%
1559
March1st to 15thNight
44%
764
14%
2246
11%
764
48%
764
20%
1625
March16th to endNight
41%
768
10%
2089
6%
767
43%
767
16%
1620
April1st to 15thNight
42%
599
12%
1679
7%
599
45%
599
18%
1257
April16th to endNight
41%
540
11%
1620
10%
540
44%
540
18%
1161
May1st to 15thNight
45%
377
7%
1302
6%
377
47%
377
18%
892
May16th to endNight
42%
374
0%
1309
0%
374
42%
374
15%
918
June1st to 15thNight
44%
360
0%
1260
0%
360
44%
360
13%
938
June16th to endNight
51%
360
0%
1089
0%
360
51%
360
19%
775
July1st to 15thNight
61%
340
0%
1151
0%
340
61%
340
22%
748
July16th to endNight
57%
376
3%
1239
2%
354
58%
354
21%
787
August1st to 15thNight
65%
368
6%
1393
8%
366
66%
366
22%
850
August16th to endNight
57%
573
12%
1719
11%
573
58%
573
27%
1118
September1st to 15thNight
59%
626
15%
1772
12%
626
60%
626
32%
1105
September16th to endNight
55%
716
19%
1980
13%
716
59%
716
33%
1240
October1st to 15thNight
44%
720
14%
2153
9%
720
47%
720
21%
1499
October16th to endNight
40%
772
14%
2500
10%
772
47%
772
19%
1721
November1st to 15thNight
34%
950
12%
2699
8%
950
39%
950
15%
2078
November16th to endNight
32%
975
9%
2925
5%
975
36%
975
14%
2271
December1st to 15thNight
34%
975
10%
2925
6%
975
37%
975
14%
2237
December16th to endNight
38%
1040
12%
3120
6%
1040
43%
1040
17%
2311

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

Occurrence of each ForecastData
Points
Cloud CoverDay
11%9%47%6%35%5%6%8%31%
49688
Night
9%9%48%7%45%5%6%7%30%
49122
TransparencyDay
48%8%18%18%5%
49338
Night
49%8%16%18%6%
48976
SeeingDay
15%420%31%21%6%
6769
Night
14%424%35%18%2
15976

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings:
Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
6%11%6%11%10%5%5%46%7%23%
1358
16th to endDay
6%14%5%9%9%35%5%5%7%26%
1528
February1st to 15thDay
8%13%6%10%7%45%46%7%26%
1543
16th to endDay
412%7%11%8%46%6%6%7%23%
1572
March1st to 15thDay
8%13%6%10%9%345%6%7%23%
1950
16th to endDay
12%12%6%8%6%45%5%6%9%22%
2130
April1st to 15thDay
12%10%47%6%36%5%5%7%29%
2269
16th to endDay
13%13%36%5%35%6%5%8%28%
2340
May1st to 15thDay
10%8%37%6%46%5%6%8%33%
2649
16th to endDay
17%7%36%6%26%5%5%7%30%
2802
June1st to 15thDay
17%8%48%7%46%5%6%6%26%
2700
16th to endDay
14%7%25%6%46%6%7%8%31%
2866
July1st to 15thDay
11%5%25%6%35%5%6%9%36%
2736
16th to endDay
10%4145%45%5%7%9%40%
2846
August1st to 15thDay
10%6%25%436%6%7%10%36%
2558
16th to endDay
8%5%25%5%4447%10%41%
2483
September1st to 15thDay
12%7%25%5%345%5%8%40%
2187
16th to endDay
11%4245%3446%8%43%
1980
October1st to 15thDay
13%9%47%6%35%445%33%
1806
16th to endDay
11%10%47%5%245%7%8%30%
1711
November1st to 15thDay
8%12%6%10%7%36%5%5%7%26%
1488
16th to endDay
6%12%6%10%6%445%6%6%29%
1365
December1st to 15thDay
6%13%6%11%9%5%6%5%46%22%
1365
16th to endDay
5%11%5%10%9%5%7%5%6%8%23%
1456
January1st to 15thNight
7%12%6%10%8%5%6%5%5%7%24%
2910
16th to endNight
7%13%5%9%8%4445%7%29%
3058
February1st to 15thNight
6%10%5%12%9%36%5%5%5%28%
2640
16th to endNight
7%11%5%7%6%46%6%6%8%29%
2185
March1st to 15thNight
8%8%49%6%46%6%6%8%29%
2246
16th to endNight
10%11%6%9%7%36%5%7%8%21%
2088
April1st to 15thNight
10%9%49%7%47%5%6%6%29%
1679
16th to endNight
14%10%27%6%45%46%6%31%
1620
May1st to 15thNight
10%6%48%7%46%46%7%33%
1301
16th to endNight
20%8%25%6%25%5%6%7%29%
1309
June1st to 15thNight
15%8%38%6%5%6%5%7%6%25%
1260
16th to endNight
11%7%36%7%36%6%7%9%29%
1089
July1st to 15thNight
10%416%6%346%8%11%35%
1221
16th to endNight
9%435%436%5%7%11%37%
1323
August1st to 15thNight
9%415%436%46%9%42%
1400
16th to endNight
9%5%26%6%35%6%5%10%38%
1719
September1st to 15thNight
12%425%43345%8%46%
1772
16th to endNight
10%5%2442435%7%49%
1980
October1st to 15thNight
12%9%47%6%3445%6%35%
2153
16th to endNight
10%8%36%6%45%5%7%8%32%
2500
November1st to 15thNight
12%12%6%8%6%35%46%6%26%
2699
16th to endNight
7%12%6%10%8%46%5%5%6%26%
2925
December1st to 15thNight
9%12%6%10%8%4445%7%25%
2925
16th to endNight
410%5%11%8%46%5%7%9%24%
3120

Transparency (when cloud cover <= 30%)
Color Meanings:
Too cloudy to forecast Poor Below Average Average Above average Transparent
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
57%8%13%14%5%
1358
16th to endDay
54%7%12%15%7%1
1528
February1st to 15thDay
55%6%17%14%5%
1543
16th to endDay
56%7%14%16%5%
1572
March1st to 15thDay
57%7%16%15%3
1950
16th to endDay
56%8%13%16%4
2131
April1st to 15thDay
51%6%16%18%6%
2269
16th to endDay
51%7%16%16%7%1
2340
May1st to 15thDay
46%7%14%21%10%
2649
16th to endDay
50%7%14%18%8%
2807
June1st to 15thDay
55%8%16%16%3
2700
16th to endDay
47%9%20%17%4
2866
July1st to 15thDay
40%10%23%22%3
2577
16th to endDay
38%11%28%19%1
2667
August1st to 15thDay
39%12%29%15%2
2540
16th to endDay
35%9%26%22%5%
2483
September1st to 15thDay
40%8%20%22%6%1
2187
16th to endDay
36%7%20%27%6%1
1980
October1st to 15thDay
50%6%16%20%5%
1806
16th to endDay
47%7%16%24%3
1711
November1st to 15thDay
55%7%15%17%4
1488
16th to endDay
52%9%17%15%4
1365
December1st to 15thDay
62%7%10%15%3
1365
16th to endDay
56%7%13%14%8%
1456
January1st to 15thNight
57%7%17%12%41
2910
16th to endNight
52%6%14%17%6%1
3058
February1st to 15thNight
55%6%15%15%6%
2651
16th to endNight
48%8%15%18%7%1
2185
March1st to 15thNight
48%8%14%20%6%
2246
16th to endNight
56%7%12%17%5%
2091
April1st to 15thNight
53%7%13%17%7%1
1679
16th to endNight
49%8%11%17%11%1
1620
May1st to 15thNight
47%7%11%18%13%1
1302
16th to endNight
52%6%12%17%8%2
1309
June1st to 15thNight
54%9%14%17%4
1260
16th to endNight
46%10%21%17%3
1089
July1st to 15thNight
37%12%22%21%5%
1151
16th to endNight
38%11%23%23%2
1239
August1st to 15thNight
35%11%28%21%2
1393
16th to endNight
38%8%21%24%6%
1719
September1st to 15thNight
36%5%19%28%9%1
1772
16th to endNight
32%8%16%28%11%2
1980
October1st to 15thNight
47%6%15%22%7%
2153
16th to endNight
45%9%18%21%5%
2500
November1st to 15thNight
56%7%11%18%4
2699
16th to endNight
56%9%14%13%41
2925
December1st to 15thNight
57%7%14%15%5%
2925
16th to endNight
53%6%16%16%6%
3120

Seeing (when cloud cover <= 80%)
Color Meanings:
Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
MonthDays in MonthOccurrence of each ForecastData
Points
January1st to 15thDay
10%5%13%41%25%4
90
16th to endDay
10%220%41%15%9%
96
February1st to 15thDay
9%5%27%34%18%5%
96
16th to endDay
13%216%37%24%6%
153
March1st to 15thDay
13%328%35%14%4
312
16th to endDay
19%219%31%24%2
288
April1st to 15thDay
18%7%21%33%15%2
269
16th to endDay
24%5%20%30%13%5%
270
May1st to 15thDay
11%7%22%32%20%5%
444
16th to endDay
19%5%15%32%19%7%
517
June1st to 15thDay
18%5%22%29%18%5%
495
16th to endDay
15%420%28%23%7%
661
July1st to 15thDay
11%216%31%30%7%
511
16th to endDay
13%418%30%27%5%
515
August1st to 15thDay
14%114%27%26%14%
362
16th to endDay
12%5%21%30%25%3
332
September1st to 15thDay
18%5%24%24%21%6%
315
16th to endDay
14%9%26%25%19%4
315
October1st to 15thDay
27%422%25%14%6%
183
16th to endDay
20%7%25%27%16%2
144
November1st to 15thDay
20%324%38%11%2
125
16th to endDay
12%228%35%13%7%
90
December1st to 15thDay
10%6%25%32%21%4
90
16th to endDay
7%120%39%23%7%
96
January1st to 15thNight
13%5%26%35%14%3
975
16th to endNight
14%8%28%32%14%1
978
February1st to 15thNight
12%423%38%18%2
764
16th to endNight
12%322%36%20%3
684
March1st to 15thNight
12%325%40%15%3
764
16th to endNight
15%422%35%19%2
768
April1st to 15thNight
14%6%23%36%19%1
599
16th to endNight
19%424%34%16%1
540
May1st to 15thNight
15%321%40%17%1
378
16th to endNight
22%418%31%21%2
375
June1st to 15thNight
19%5%20%35%15%3
360
16th to endNight
14%317%34%28%1
360
July1st to 15thNight
12%115%43%25%
340
16th to endNight
11%219%37%25%2
376
August1st to 15thNight
10%113%32%34%6%
368
16th to endNight
9%319%39%26%1
573
September1st to 15thNight
13%116%40%25%2
626
16th to endNight
12%421%42%16%2
716
October1st to 15thNight
18%224%34%17%1
720
16th to endNight
16%429%36%13%
772
November1st to 15thNight
18%6%28%33%11%2
950
16th to endNight
13%6%30%33%12%2
975
December1st to 15thNight
15%8%26%30%16%3
975
16th to endNight
9%328%36%18%4
1040
Page generated at 2018-03-12 11:28:09. Version ac04

Copyright 2018 A. Danko


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